A hard, silvery metal with a blue tinge. Chromium is used to harden steel, to manufacture stainless steel (named as it won’t rust) and to produce several alloys. Chromium plating can be used to give a polished mirror finish to steel. Chromium-plated car and lorry parts, such as bumpers, were once very common.
Chromium (Cr), chemical element of Group 6 (VIb) of the periodic table, a hard steel-gray metal that takes a high polish and is used in alloys to increase strength and corrosion resistance.
Chromium was discovered (1797) by the French chemist Nicolas-Louis Vauquelin and isolated as the metal a year later; it was named for its multicoloured compounds. The green colour of emerald, serpentine, and chrome mica and the red colour of ruby are due to small amounts of chromium.
The name of the element chromium (from Greek chrōmos, “colour”) connotes the pronounced and varied colorations of chromium compounds.
Uses of Chromium
- Chromium is used to harden steel, make stainless steel (named because it does not rust) and make various alloys.
- Chrome plating can be used to give steel a highly polished finish. Chrome-plated car and truck parts such as bumpers were once common. Chrome plating of plastics, which are often used in bathroom fittings, is also possible.
- About 90% of all leather is tanned with chrome. However, the wastewater is toxic, so alternatives are being studied.
- Chromium compounds are used as industrial catalysts and pigments (in light green, yellow, red and orange colors). Rubies get their red color from chrome, and glass treated with chrome is emerald green in color.
- In metal ceramics.
- In chrome plating.
- As dyes and paints.
- To produce synthetic rubies.
- In alloys, e.g., stainless steel.
- To manufacture molds for the firing of bricks.
- As a catalyst in dyeing and tanning of leather.
- In metallurgy to provide corrosion resistance and a shiny finish.
Uses of compounds
- Chromium (IV) dioxide (CrO2) is a magnetic compound. It’s ideal shape anisotropy, which imparts high coercivity and remnant magnetization, made it a compound superior to γ-Fe2O3. Chromium (IV) oxide is used to manufacture magnetic tape used in high-performance audio tape and standard audio cassettes.
- Chromium (III) oxide (Cr2O3) a green pigment (coloring agent) in paint, asphalt roofing, and ceramic materials; refractory bricks; abrasive.
- Chromic acid is a powerful oxidizing agent and is a useful compound for cleaning laboratory glassware of any trace of organic compounds. It is prepared by dissolving potassium dichromate in concentrated sulfuric acid, which is then used to wash the apparatus. Sodium dichromate is sometimes used because of its higher solubility (50 g/L versus 200 g/L respectively). The use of dichromate cleaning solutions is now phased out due to the high toxicity and environmental concerns. Modern cleaning solutions are highly effective and chromium free.
- Potassium dichromate is a chemical reagent, used as a titrating agent.
- Chromates are added to drilling muds to prevent corrosion of steel under wet conditions.
- Chrome alum is Chromium (III) potassium sulfate and is used as a mordant (i.e., a fixing agent) for dyes in fabric and in tanning.